A large number of methods and compositions for beautifying and strengthening the nails of humans are well known. Prior art methods include coating the nail of an animal, including humans with a composition including a film-forming polymer and additional ingredients such as pigment, plasticizer and solvents or alternatively, attaching preformed artificial nails to human nails with adhesives. Additional methods include adding crosslinkable polymers to nail coating compositions to mend, strengthen and elongate natural nails and repairing nails with a fabric patch.
Most nail enamel compositions presently on the market or disclosed in the prior art dry in five minutes or longer. Even those nail enamels that claim to be quick-dry, i.e., dry in about five minutes, are often not truly dry but rather are only dry to the touch. When a purportedly "dry" nail enamel of the prior art brushes up against a hard surface, the nail enamel often smudges, leaving tack.
One nail polish drying composition disclosed in U.S. Pat. No. 4,798,720 prepared from commercially available top coat nail polish, acrylic nail powder, acrylic nail primer and the adhesive "crazy glue" is described as being used in combination with commerically available colored nail polishes to alter the drying time of the nail polish to a period of more than three minutes. The compositions of this patent are used as base coats in combination with commercially available pigment containing nail polishes. The patent claims to dry from one to seven coats of pigment containing nail polish within a period ranging from about three to five minutes. This composition functions as a base coat or top coat and unlike the composition of the present invention, must be used in combination with a commerically available pigment nail polish to provide a lasting pigmented nail enamel finish.
A nail polish which can be used to coat a natural or synthetic nail which dries in less than three minutes without requiring an additional application of a base coat or top coat as is disclosed in the prior art would be very desirable. Nail polishes which dry in a period of less than 150 seconds would be even more desirable, as would polishes that dry in periods less than about 90 seconds. A nail polish composition which would dry in a period of no greater than about 60 seconds would be especially useful in situations where "drying" time is important.
Working women need to have a product which can be easily applied and which dries in the shortest amount of time to avoid a situation where they are simply wasting precious time waiting for their nail polish to dry. In the manicure and pedicure industries, a pigmented nail polish composition which can dry in a period less than three minutes would provide a significant advantage over the prior art compositions.
Solvent mixtures for nail enamels of the prior art have covered a wide range of compositions and have included as many as six or seven solvents to control flow, viscosity, evaporation rate and drying time of the enamel. As discussed in Peirano, "Nail Lacquers and Removers", Cosmetics Science and Technology, Interscience Publishers, Inc., 1957, solvent or mixed solvents used as the volatile portion of nail enamels are of prime importance because of their direct effect on ease of application of enamel, on the rate of drying and hardening, on the viscosity of the enamels and on the characteristics of the final film. According to this reference, too rapid a rate of evaporation causes a poor flow of the enamel and also gives an uneven, streaky application. The reference also cites the importance of proper solvent balance during the drying stages of the lacquer. In general, due to the wide differences in evaporation rates of the solvents which are included in the prior art compositions, these compositions undergo many changes during the drying of the film. For example, during the course of evaporation of the solvent from the nail enamel on the nail, differential evaporation of the solvents within the composition may result in the presence of higher concentrations of certain solvents during drying, which in turn creates precipitation of the film forming polymer, resin and/or plasticizer, thereby destroying the integrity of the film and the appearance of the enamel. If the solvent becomes too lean to maintain the solubility of the resin in solution, the resin will precipitate, also resulting in unacceptable results.
Another reference which provides insight into the solvent mixtures useful in nail enamels and briefly touches the subject of drying time is an article by Harvey M. Remz, Cosmetics and Toiletries, Vol. 103, 70 (1988). In this reference, Mr. Remz points out that providing solvent balance is a complex task in formulating a nail enamel composition and briefly discusses evaporation rate and the volatility of solvents included in nail polish on page 76.
The complicated character of the nail enamel mixtures of the prior art and the many possible combinations of volatile and nonvolatile components had, until the unexpected discovery of the present invention, made the determination of a proper solvent balance from the perspective of viscosity, solubility of the individual components and the acceptability of the deposited enamel (gloss) in combination with a drying time of less than three minutes virtually impossible. Until the discovery of the present invention, the identification of the evaporation rates of the individual solvents under various conditions had not removed the uncertainty involved in determining a suitable solvent balance incorporating quick-drying characteristics. Although the desirability of a quick drying nail enamel has been a long-felt need, the rate of drying of the nail enamels of the prior art has been limited by the aforementioned considerations. Thus, before the discovery of the present invention, simply incorporating low boiling solvents did not increase the likelihood that an acceptable solvent system for nail enamels would be found or that one could obtain a nail enamel composition which dried in under three minutes. In the present invention, the use of acetone in certain weight percentages of the composition, in combination with numerous solvents which provide acceptable viscosity, creates a consistent quick-drying solvent system which provides the nail enamel with favorable characteristics of drying time, viscosity, gloss, flexibility and durability.
Acetone, also known as 2-propanone, dimethylketone and beta-ketopropane is a volatile solvent which has a boiling point of 56.5.degree. C. and is miscible with an extremely large number of solvents including water, alcohol, dimethylformamide, chloroform, methylene chloride, toluene, esters, including methylacetate and ethylacetate, benzene and toluene, ethers and numerous oils and hydrocarbons, among others. A number of prior art references disclose acetone as one of a large number of solvents which are useful for formulating nail enamels. The uniqueness of acetone for use in the present invention resides in the fact that acetone will interact with solvents used in nail enamel preparations of the present invention to produce a solvent system which evaporates in under three minutes and instills acceptable characteristics which are desired in nail enamels.
It has surprisingly been discovered that the inclusion of specific weight percentages of acetone in combination with additional solvents including wetting agents and diluents in compositions for coating natural and synthetic nails containing organoclay thixotropic agents produces a nail coating composition which dries in a period of time less than three minutes and produces a coating on a nail which is hard, flexible and has good wear characteristics including durability and high gloss. Moreover, the use of acetone in the volatile component of nail enamel compositions of the present invention within specific weight percentages provides a consistent basis upon which one of ordinary skill in the art may modify nail enamel compositions according to the present invention without dramatically adversely affecting the drying time of the nail enamel and without dramatically adversely affecting other characteristics which are required for commercially competitive nail enamels.